Minor performance improvements

Based on profiling 32-bit Windows release.  Probably helps ARM/etc. a tiny bit too but, can never say...

 * Gets rid of resched sprintf()'ing. (~0.5%)
 * Copies thread context in larger blocks. (~1%)
 * Skips a map.find() call. (~0.2%)

Nothing major (and percentages are probably much smaller on arm vs. Comp_Generic), but noticed the resched in the profiler and had a note in my todo about it already.

-[Unknown]